Researchers at Purdue University have created a patent-pending method of producing filaments that can be used to manufacture sensing plastic structures. The technology basically transforms plastic structures into functional strain gauges, which are usually manufactured with thin metal foils.
Dispersed Particles
The research team from the School of Engineering Technology in the Purdue Polytechnic Institute, and the School of Aeronautics and Astronautics in the College of Engineering, at Purdue developed a means of blending electrically conductive particles into plastic FDM filaments, while enabling the particle are evenly distributed throughout the filaments.
Normal strain gauges are applied to the external surfaces of structures to monitor strain as loads interact with the structure in question. The problem is, that when the structural member is bending, the sensor is only measuring the strain at the surface – it gives no indication of what is happening inside the structural member.
By making structures able to sense strain throughout, anyone monitoring the structure will be able to gain insights into mechanical behavior beneath the surface.
“Generally, we apply that strain gauge across the full part or apply it to the top and bottom of the part to get information on overall strain across the part,” said Brittany Newell, assistant professor from the Purdue Polytechnic Institute.
“However, the middle and internal structures are never monitored since the gauges are glued to the surface.”
The patented wet-mix process takes conductive particles and polymer pellets, mixes them together and adds them to a filament extruder. The extruder produces the filament, and specimens are cut for conductivity measurements. The filaments are then pelletized before being printed.
Durable Sensors
Because the conductive particles are so small, they allow the plastic matrix to retain its strength after printing.
“The results from this work enable users to create complex 3D structures with embedded strain gauges, rapidly moving traditional prototype pieces into fully functional and structurally assessable parts,”
“A limitation of application of 3D printed parts has been in their durability. With this development, we can continually monitor the structural health of the part with the sensor embedded in the print.”
The sensors can also be tuned by adjusting the electrical and mechanical properties to provide tailored responses, which can then allow the sensor to be optimized for particular applications.
These particular researchers have been fairly active in the development of making sensing plastics, and have previously published papers on turning plastics into other functional sensors such as temperature sensors and pressure sensors.
There are numerous applications for such devices, including in IoT devices, aerospace, and robotics.
The team plans to scale up the process and is looking for industry partners to assist with commercialization and integration with industrial 3D printers.
“The range of items that can be produced with these filaments is broad, and testing should be done to expand to new prototypes,” said Newell.
